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Ozone depletion

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Ozone (O3) is an atmospheric gas found mainly in the upper atmosphere. The ozone layer forms a natural screen that absorbs most of the ultraviolet (UV) radiation from sunlight – before it reaches the earth’s surface.

Some human activities release chemicals into the air that remove ozone. Less ozone in the atmosphere increases the amount of ultra-violet (particularly UV-B) rays that reach the earth. Sunburning UV-B is harmful to people and the environment.

The hole in the ozone

During the 1980s and 1990s there was a decreasing trend in the ozone concentration over New Zealand. This has stabilised since the 2000s, similar to international trends.  

During early spring, an ozone ‘hole’ has formed over Antarctica since the late 1970s. Although the hole itself doesn’t move, when the ozone layer rebuilds itself during late spring and early summer the total ozone layer over the Earth gets diluted (reduced).

Effects of reduced ozone

In New Zealand it’s estimated that ozone losses since 1980 have caused sunburning ultraviolet (UV) radiation to increase by 10 to 12 per cent (1996 levels). This has a flow-on of increase in effects:

  • Health problems for people and animals - more skin cancer, eye damage and damage to the immune system (increasing vulnerability to diseases).
  • Reduced plant growth - increased UV radiation can reduce plant photosynthesis and growth.
  • Genetic changes - small organisms may have an increased chance of mutation.
  • Damage to possessions - materials sensitive to ultra-violet light may age quicker.

Ozone-destroying chemicals

Ozone naturally breaks down and re-forms itself in the upper atmosphere. However, except for areas near the equator, ozone is now being destroyed much faster than it’s being created.

The main culprits are synthetic (human-made) chemicals containing bromine and chlorine, such as chlorofluorocarbons (CFCs). CFCs were used as refrigeration agents and propellants in aerosol sprays. Some existing refrigeration systems still contain this chemical.

Other ozone-depleting chemicals include:

  • carbon tetrachloride
  • methyl bromide
  • methyl chloroform
  • halons
  • hydrobromofluorocarbon
  • hydroflurocarbons.

These chemicals have a range of uses, for example, methyl bromide is used as a fumigant for treating primary products for export such as timber (and imported products) to control quarantine pests.

Protecting the ozone layer

In 1998 the New Zealand Government adopted the Montreal Protocol on 'Substances which Deplete the Ozone Layer'. This international protocol called for a freeze of annual use of CFCs to 1986 levels and a reduction in use by 50 per cent by 1999.

New Zealand’s Government controls the import and sale of CFCs and halons, and technology and goods made using CFCs. 

You can also help to reduce the amount of CFCs entering the atmosphere:

  • Dispose of your old refrigerator properly to make sure CFCs aren’t released into the air - recycling depots usually have a place for old refrigerators.
  • Maintain your car’s air conditioning system so it doesn’t leak CFCs.

More information

  • Ministry for the Environment - Ozone Layer Protection Act 1996
  • National Institute of Water and Atmospheric Researchs (NIWA) - UV and ozone
  • Sunsmart - information on how to protect yourself from UV rays. New Zealand has a very high rate of melanoma, the deadliest form of skin cancer.